1. Field of the Invention
This invention relates to a digital display system utilizing a variable color display.
2. Description of the Prior Art
Commercially available display devices with monochromatic digital readout are capable of displaying digital values at a relatively fast rate. However, to determine a significance of each displayed value, an operator must rapidly read displayed values and perform mental comparisons with predetermined limits. The task is much more complicated when the limits are variable.
A light emitting diode display, disclosed in U.S. Pat. No. 4,488,149, issued on Dec. 11, 1984 to William A. Givens, Jr, is capable of displaying digits in two different colors, in accordance with different color control signals.
A driving circuit for light emitting diodes, described in U.S. Pat. No. 3,740,570 issued on Jun. 19, 1973 to George R. Kaelin et al., utilizes special light emitting diodes that emit light of different colors in response to different currents.
A method and apparatus for independent color control of alphanumeric display and background therefor are disclosed in U.S. Pat. No. 3,911,418, issued on Oct. 7, 1975 to Minoru Takeda. In order to exhibit a character in a desired color, the code of a character and its color code are entered from a keyboard. A color code for the background area is then entered from the keyboard, independently of the color code for the displayed character. All entered codes are then encoded into a composite train of pulses, which are then separated, decoded, and used for exhibiting on a cathode ray tube display device the desired character in the desired color, and for controlling color of its background. Takeda does not consider that the color of the display background may be automatically controlled in accordance with a relation of an exhibited digital value to a limit.
A prior art display system capable of comparing an exhibited digital value with a limit and of automatically indicating their relationship is unknown to the inventor.